ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 295 



the leaf is terminal. The greatest possible reduction of the female 

 flower occurs only in the Coniferre (Podocarpeaa, Araucaria). 



Axillary iBuds of the Hornbeam.* — J. Velenovsky points out a 

 peculiarity noted in a specimen of Carpinus Betulus, indicating that the 

 stipules may sometimes usurp the function of leaves, and that they may 

 then form buds in their axils which must be regarded as serial trans- 

 verse buds. 



Translucency of Leaves, f — Dr. L. Linsbauer has constructed an 

 apparatus which he calls a diaphanometer for registering the proportion 

 of sunlight (especially the more refrangible rays) which passes through 

 the leaves ; the computations being founded on the lines proposed by 

 Wiesner.f The leaves of the same plant differ in their degree of trans- 

 lucency according as they are exposed to the sun or develop in the 

 shade ("sun-leaves" and "shade-leaves" respectively). The former 

 are as a rule smaller and thicker, often crumpled or rolled back at the 

 margin ; while the latter are larger and thinner, and usually flat. Both 

 sun- and shade-leaves differ greatly among one another in their trans- 

 lucency. Among sun-leaves the extent of variation in this respect is 

 20 : 1 ; among shade-leaves 7:1; but the most translucent sun-leaf 

 allows only one-third of the light to pass as compared with the most 

 translucent shade-leaf. The more typical the structure of a shade-leaf,, 

 the greater is its translucency. The average proportion of sunlight 

 which passes through green leaves is • 05-0 ■ 06 (5-6 p.c.) ; while with 

 colourless leaves or portions of leaves it is as high as 0-32 (32 p.c). 



Morphology of Tropical Leaves.§ — C A. M. landman describes the 

 form and structure of a number of plants in Paraguay and Brazil which 

 adapt them to the conditions of the climate and of the habitat. In the 

 genus Alophia and some other species of Iridese, the leaves have a number 

 of longitudinal ridges which protect them from too great insolation, and 

 serve also to retain the rain and dew by capillary attraction. In the 

 deep forests the dwarf trees and shrubs have mostly a slender growth 

 with narrow undivided leaves, of an intense green colour which adapts 

 them to the dim daylight. Two genera, Bomarea (Alstroemeriacese) 

 and Pharus (GramineaB) are described with resupinate leaves, due to a 

 torsion of the petiole of 180°. The lianes have mostly cordate acuminate 

 leaves, with glabrous surface, allowing the abundant rain to flow freely 

 from them. 



Underground Leaves. || — J. Thomas has studied the structure of 

 underground leaves or scales as contrasted with those formed in normal 

 positions exposed to the light and air. They are classified as follows : — 

 Scales corresponding to sheaths; to sheathing petioles; to ordinary 

 petioles ; to the lamina of a leaf. As a rule the underground scale has, 

 on transverse section, more or less the form of a crescent or of a triangle ; 

 its thickness is, in Monocotyledons, generally greater than that of the 



* Oesterr. Bot. Zeitschr., 1. (1900) pp. 409-11 (1 fig.), 

 t Beih. z. But. Centralbl., x. (1901) pp. 53-89, 143. 

 j Cf. this Journal, 1899, p. 299. 



§ Bih. k. Svensk. Vetensk.-Akad. Handl., xxv. (1S99) 63 pp. and 20 figs. See 

 Bot. Centralbl., lxxxv. (1901) p. 41. 



H Bev. Gen. de Bot. (Bonnier), x ii. (1900) pp. 369-93, 417-33 (1 pi. and 10 figs.). 



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